Beneficiating agent composition

ABSTRACT

The present invention relates to compositions of matter which are especially useful as beneficiating agents in the production of well drilling muds. These compositions comprise mixtures of carboxylic acid polymers and metal salts which mixtures are water soluble at a pH of less than 7.0 wherein the metal is selected from Groups IB, IIB, VIB, VIIB and VIII of the Periodic Table and lead.

This is a Division of application Ser. No. 250,619, filed May 5, 1972and now U.S. Pat. No. 3,816,308.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to compositions of matter which are usefulas beneficiating agents for clays used in the production of welldrilling muds.

2. Description of the Prior Art

Clay beneficiating agents for well drilling muds are commonly used inthe industry in order to improve the yield of the mud. Thesebeneficiating agents and drilling muds are described at length in suchreferences as U.S. Pat. Nos. 2,948,678, 3,070,543, 3,070,544, and3,558,545, as well as in other references. In spite of the improvedyields obtained with the beneficiating agents described in the abovereferences a need exists in the art for more efficient beneficiatingagents which will give increased yields.

SUMMARY OF THE INVENTION

In accordance with the present invention a composition of matter isprovided which improves the yield of a clay used in drilling muds. Thecomposition of matter is a mixture of at least one carboxylic acidpolymer and at least one metal salt which mixture has a water solubilityof at least 1% by weight at a pH less than 7.0 wherein the metal isselected from the group consisting of lead and a metal from Groups IB,IIB, VIB, VIIB and VIII of the Periodic Table as set forth at pages 56and 57 of LANGE'S HANDBOOK OF CHEMISTRY, Ninth Edition, McGraw-Hill BookCompany, New York (1956).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The carboxylic acid polymer component of the beneficiating agents of thepresent invention is characterized by being water soluble at a pH lessthan 7 and more preferably in the pH range of from 2.0 to 6.5. Theamount of solubility should be such that the polymer will form at leasta 1% solution in water at 25° C. at a pH in the above specified ranges.

The preferred polymers are further characterized by having a numberaverage molecular weight of at least 5,000. There is no upper limit onthe molecular weight except that the practical limit is determined bythe water solubility of the polymer. Those skilled in the art realizethat higher molecular weight polymers will provide a higher solutionviscosity and more beneficiating ability at a given polymerconcentration. However, there is a practical upper limit on themolecular weight in the terms of the water solubility of the polymer andeventually a point will be reached with increasing molecular weightwhere the polymer no longer meets the solubility requirements outlinedabove.

The amount of carboxylic acid groups in the polymer is in the range offrom 20 mol percent to 100 mol percent and more preferably 40 molpercent to 100 mol percent based on the total polymeric composition.These polymers are the homopolymerization products of carboxylic acidmonomers such as acrylic acid, methacrylic acid, etc. Alternately, thepolymers are interpolymerization products of at least one carboxylicacid monomer and at least one other monomer which is copolymerizabletherewith. Examples of the carboxylic acid monomer used in theinterpolymers include acrylic acid, methacrylic acid, maleic anhydride,maleic acid, fumaric acid, crotonic acid and itaconic acid, mesaconicacid, citraconic acid, etc. Examples of monomers which arecopolymerizable with the carboxylic acid monomer include lower alphaolefins containing from 2 to 4 carbon atoms such as ethylene, propylene,butylene, isobutylene, alkyl vinyl ethers wherein the alkyl groupcontains 1 to 4 carbon atoms such as vinyl methyl ether, vinyl ethylether, vinyl propyl ether, vinyl butyl ether, vinyl isobutyl ether;vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate,vinyl butyrate and vinyl benzoate; esters of acrylic and methacrylicacid wherein the alcohol moiety of the ester contains from 1 to 8 carbonatoms such as methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate,methyl methacrylate, ethyl methacrylate, 2-ethylhexyl methacrylate;vinyl aromatic monomers such as styrene, alpha-methyl styrene,chlorostyrene, vinyl toluene, etc.; amide type monomers such asacrylamide, methacrylamide, alkylol acrylamides such as methylolacrylamide, ethylol acrylamide, methylol methacrylamide, ethylolmethacrylamide, methylol ethacrylamide, ethylol ethacrylamide, etc.;N-methylolated acrylamides and the N-methylolated methacrylamides whichare etherified with a lower alkanol such as methanol, ethanol, propanoland butanol, etc. Care must be taken in the choice of comonomer and theamount thereof so that the above requirement of water solubility is met.

Preferred polymers for use in the present invention are poly(vinylacetate-maleic anhydride), poly(ethylene-maleic anhydride), poly(vinylmethyl ether-maleic anhydride) and polyacrylic acid.

The metal salt component of the beneficiating agents of the presentinvention is selected from water soluble organic and inorganic metalsalts of lead and metals of Groups IB, IIB, VIB, VIIB and VIII of thePeriodic Table. The solubility is such that the salt will form at leasta 1% solution in water at 25° C. at a pH less than 7.0. These includewater soluble inorganic sulfates, nitrates and chlorides as well asmetal salts of aliphatic monocarboxylic acids such as formic, acetic,propionic, n-butyric, isobutyric, etc. Preferred are organic acid saltsof aliphatic monocarboxylic organic acids containing from 1 to 4 carbonatoms, where the metal is selected from the group consisting of zinc,chromium, nickel, manganese, cobalt and lead. Especially preferred arethe formates and acetates of zinc, chromium, nickel, manganese, cobaltand lead.

The amount of water-soluble metal salt used in the beneficiating agentsof the present invention is in the range of from 5 to 80% by weightbased on the total weight of polymer and metal. More preferably, theamount of salt is in the range of from 5 to 70% by weight. Conversely,the amount of polymer in the beneficiating agent is in the range of from95 to 20% and more preferably 95 to 30% by weight.

The amount of beneficiating agents (polymer and salt) used in thepresent invention depends to some extent on the degree of beneficiationdesired and varies with the clay. Generally, only very small quantitiesare required and amounts within the range from about 0.1 to about 10 lb.per ton of clay will produce satisfactory results. The preferredquantities for treatment are from about 1.5 to 3.5 lb. of beneficiatingagent per ton of clay. In general, the yield obtainable at aconcentration of 3 lbs. of the interpolymers per ton of clay lies in therange from 160-190 barrels. With some clays, yields as high as 270barrels have been achieved by increasing the concentration to 3.5lb./ton of clay. In some instances, a maximum yield of 150 barrels isobtained with 1.5 lb. of the interpolymers per ton of clay and furtheraddition results in a decrease in yield value.

The beneficiating agents of the present invention are prepared by dryblending the polymeric and metal salt components, by mixing aqueoussolutions of these components or by dissolving one component in asolution of the other component. Alternately, the polymeric and metalsalt components may be dry blended with the clay or added to clayslurries which may already contain the other component. Other methodswell known to those skilled in the art may also be used.

A preferred embodiment of the present invention calls for the use of aflocculating agent in combination with the clay beneficiating agents ofthe present invention. The flocculating agents are used in amounts offrom 0 to 100% by weight based on the weight of the polymeric componentof the beneficiating agent. Examples of these flocculating agents, whichare well known in the art, include polyacrylamide, starch and starchderivatives, polyethylene oxide, polyacrylic acid, etc.

The clays which are used in well drilling operations are well known tothose skilled in the art. Especially preferred are the montmorilloniteand bentonite clays. Species of these clays include beidellite,nontronite, hectorite and saponite. Some of these clays are presentlytoo expensive for use in drilling muds, but nevertheless are susceptibleto having their yield increased by the practice of this invention. As apractical matter, the invention will find its widest application inconjunction with the beneficiation of bentonite or montmorillonite.These clays, in the raw state, usually have a rather low yield of theorder of 30 to 35 barrels per ton and will desirably be beneficiateduntil the yield exceeds 90 barrels per ton so as to meet the minimumspecifications of many purchasers.

The beneficiating agents of the present invention can be added to theclay in any desired manner. In general, a simple mechanical mixture ofthe clay and beneficiating agent is prepared by dry-blending thebeneficiating agent in powder form directly with dry clay. This can bedone conveniently at the time the clay is ground in a roller mill, forexample. Alternatively, an aqueous solution of the beneficiating agentmay be sprayed directly onto the clay either in stock piles, aftercrushing, during the grinding operation, or during a bag-packingoperation. Also, if desired, the clay and beneficiating agent can beseparately added in any desired order to form a slurry. This type of wetmixing could be employed, for example, at the well site.

The "yield" of a clay such as bentonite is expressed as the number ofbarrels of 15 centipoises mud which can be prepared from one ton ofclay. The effectiveness of polymers in increasing yield is determined byadding 0.05 pound of the polymer per barrel of bentonite dispersions andthen determining the yield. Solutions of one percent by weight of thepolymers are used to insure adequate mixing of the polymer in the mudand to avoid the weighing of the small quantities of polymer required.The concentration of bentonite used is 2.8 and 4 percent by weight, or10 and 14 pounds per barrel. The bentonite is added to 350 millilitersof water in a quart jar. It is then mixed on a Hamilton Beach Mixer,Model 30, at approximately 12,000 r.p.m. for a total of 20 minutes.After 10 minutes of mixing, any bentonite which is on the sides of thejar is scraped back and mixing is continued for 5 minutes. The polymeris then added, generally 5 cc. of a 1 percent solution (0.05 pound perbarrel) and the mud is mixed for the remaining 5 minutes. The propertiesare measured immediately after mixing, a Fann viscometer being used, andthe fluid loss is also determined. To calculate the yield the logarithmof the apparent viscosity (1/2 of the 600 r.p.m. Fann reading) isplotted against the clay concentration in pounds per barrel. From theplotted data, the clay concentration required to give a viscosity of 15cps. is determined. The yield in barrels per ton is calculated by thefollowing equation:

    Y = 2.3 + (2000/c)

Where:

Y = yield in barrels per ton.

c = clay concentration in pounds per barrel.

The basic method used to evaluate polymers for flocculation of low-yieldclay is as follows: 4.0 grams of clay are added to approximately 90milliliters of water in a stoppered 100-milliliter graduated cylinder.The clay-water mixture is thoroughly mixed by shaking, then is made upto 99 milliliters with water. 1.0 Milliliter of the polymer solution (1percent by weight) is added and the mixture agitated for 1 minute byinverting the cylinder. The cylinder is then placed in an uprightposition and the timer started. The height (in milliliters) of theinterface between the clear water and the flocculated settling solids isread and recorded at the following time intervals, 10 seconds, 30seconds, 50 seconds, 80 seconds, 100 seconds, 140 seconds, 200 seconds,and 400 seconds. The logarithm of the time is plotted against the heightof the interface. From the curve drawn, the time to obtain 50milliliters of settling is determined and reported. The height of thesolids after 10 seconds, will give somewhat of a measure of the time forthe flocs to form and the 400-second reading will indicate the flocsize.

Several methods can be used to prepare the improved drilling muds of thepresent invention. The beneficiating agent or the components thereof canbe sprinkled dry over the mud pit. The beneficiating agent or componentsthereof can also be added through a hopper to the flowing mud stream. Itis very much preferred, however, to prepare an aqueous solution of thebeneficiating agent in a concentration of about 1 percent by weight.This solution is then added intermittently, or preferably continuously,to the mud system. The point of addition is usually at the point wherethe mud enters the well or leaves the mud pit. In some cases,introduction at other points, or at multiple points is advisable.

The following examples are set forth in illustration of the presentinvention and should not be construed as a limitation thereof. All partsand percentages given are by weight unless otherwise indicated.

EXAMPLE 1 (CONTROL)

This example is set forth to illustrate the beneficiating agents of theprior art. The beneficiating agent used in this example is as follows:

poly(vinyl acetate-maleic anhydride) (1):55 parts

polyacrylamide (2):10 parts

soda ash (sodium carbonate):28 parts

calcium hydroxide:7 parts

Yield tests as described above, are carried out using the foregoingbeneficiating agent in combination with five different grades ofbentonite clay which are abitrarily designated A to E. The results ofthese tests are listed in Table 1 below along with the results of aflocculation test.

EXAMPLE 2

This example is set forth to illustrate the improved beneficiatingagents of the present invention. Example 1 is repeated here using thesame polymer and same flocculating agent except that zinc acetate isused in place of the soda ash and calcium hydroxide used in Example 1.The beneficiating agent used in this example is as follows:

poly(vinyl acetate-maleic anhydride):55 parts

polyacrylamide:10 parts

zinc acetate:35 parts

Yield tests are carried out as above and the results are reported inTable 1 below along with the results of a flocculation test.

                  TABLE 1                                                         ______________________________________                                        SUMMARY OF YIELD TESTS FOR EXAMPLES 1 and 2                                   Type of Bentonite                                                                             Yield Tests (Barrels of mud)                                  Used            Example 1   Example 2                                         ______________________________________                                        A               150         232                                               B               114         176                                               C               130         184                                               D               126         177                                               E               136         189                                               FLOCCULATION TESTS                                                            Example        Flocculation Time (Seconds)                                    ______________________________________                                        1              14                                                             2              16                                                             ______________________________________                                    

The above results indicate that the use of a mixture of a water solublecarboxylic acid polymer and a metal salt such as zinc acetate inaccordance with the teachings of the present invention provides asubstantial increase in yield of 15 cps. barrels of mud with all fivegrades of bentonite tested. Moreover, this increase is obtained with noadverse effect on the flocculating power of the polyacrylamide used inthe beneficiating agent.

EXAMPLE 3

Examples 1 and 2 are repeated here using the bentonite clay designatedas A, except that the polyacrylamide flocculating agent is omitted fromthe formulations. The purpose of this example is to illustrate that thebeneficiating agents of the present invention improve the yield of mudregardless of whether or not a flocculating agent is used. The resultsof these tests are set forth below:

    ______________________________________                                        Beneficiating Agent     Yield                                                 ______________________________________                                        Example 1 (Control)     147                                                   Example 2               210                                                   ______________________________________                                    

As is evident from the above data the beneficiating agents of thepresent invention provide a significant improvement in yieldindependently of the use of a flocculating agent.

EXAMPLE 4

Example 2 (using the bentonite designated as A) is repeated here exceptthat other water soluble metal salts are used in place of the zincacetate used in Example 2. Results of the yield and flocculation testsare set forth below:

    ______________________________________                                                       Periodic                                                                      Table            Flocculation Time                             Metal Salt     Group    Yield   (Seconds)                                     ______________________________________                                        Example I (Control)                                                                          1A, IIA  150     14                                            Manganese formate                                                                            VIIB     190     *                                             Nickel acetate VIII     186     15                                            Chromium acetate                                                                             VIB      160     14                                            Cupric acetate IB       250     20                                            Cobaltous acetate                                                                            VIII     181     16                                            Lead Acetate   IVB      181     *                                             ______________________________________                                         *test not run                                                            

EXAMPLE 5

This example illustrates the use of a water-soluble ethylene-maleicanhydride copolymer as the polymeric component in the beneficiatingagents of the present invention. The poly(ethylene-maleic anhydride)used is characterized as having a carboxylic acid content of about 50mol percent and a specific viscosity of about 2.0 as measured as a 1%solution in cyclohexanone at 25° C. The bentonite designated as A inExample 1 and 2 above, is used in this example. Three tests are carriedout using the polymer alone, the polymer with the metal salts of theprior art (Example 1) and the polymer with the zinc acetate of Example 2in accordance with the practice of the present invention. The samerelative amounts of polymer and metal salts used in Examples 1 and 2 areused here.

The results of the yield tests are set forth below:

    ______________________________________                                        Beneficiating Agent        Yield                                              ______________________________________                                        EMA Alone (∥)     100                                                EMA + soda ash + calcium hydroxide                                                                       100                                                EMA + zinc acetate         170                                                (|) EMA = poly(ethylene-maleic anhydride)                            ______________________________________                                    

EXAMPLE 6

Example 3 is repeated here except using a water soluble poly(vinylmethyl ether-maleic anhydride) copolymer, which has a carboxylic acidcontent of about 50 mol percent and zinc acetate. The yield of thissystem is 221.

EXAMPLE 7

Example 3 is repeated here except using a water soluble polyacrylic acidand zinc acetate. The yield value of this system is 269.

EXAMPLES 8-9

These examples are set forth to illustrate some of the variations in theamounts of polymer and metal salt which can be used in the practice ofthe present invention. No flocculating aid is used in these examples andthe polymer and metal salt used are the same as those used in Example 2.

    ______________________________________                                        Example Amount of Polymer                                                                           Amount of Metal Salt                                                                         Yield                                    ______________________________________                                        8       35 parts      65 parts       217                                      9       95 parts       5 parts       166                                      ______________________________________                                    

EXAMPLE 10

This example illustrates the need for using a polymeric component in thebeneficiating agent which is soluble at a pH of less than 7. A dry blendof 55 parts of the sodium salt of poly(styrene-maleic anhydride) 1:1 molratio and 35 parts of zinc acetate were dispersed in water at roomtemperature. It was not possible to test this composition (pH about 8.5)since a large amount of precipitation occurs. Lowering of the pH withhydrochloric acid results in more precipitation of the polymer which isnot soluble at a pH less than about 8.0.

One advantage of the compositions of the present invention is that theycan be used with poor grades of bentonite to increase the effectivenessof such material to a point comparable to that expected for good gradesof bentonite. This can be particularly important in relativelyinaccessible areas having readily available poor grades of bentonite,but no high-quality clays.

By use of these compositions, the viscosity of water containing a verylow concentration of bentonite can be increased and the fluid loss canbe decreased to increase the efficiency of the water when used as afracturing fluid. Due to the low concentration of bentonite, there isless tendency for the fracture to become plugged by the clay when thewell is put back on production. The same advantage applies to diluteclay slurries used opposite zones to be perforated with bullet or jetperforators.

In addition to being used as beneficiating agents for drilling muds, thecompositions of the present invention may also be used as binders forceramic materials, thickening agents, coagulants, textile sizes, cementadditives, etc.

What is claimed is:
 1. A water-soluble composition of matter to improvethe yield of a clay drilling mud, consisting essentially of a mixture of(A) from 95 to 20% by weight of a polymer of at least one carboxylicacid monomer selected from the group consisting of acrylic acid,methacrylic acid, maleic anhydride, maleic acid, crotonic acid, itaconicacid, mesaconic acid, and citraconic acid, and (B) from 5 to 80% byweight of at least one water soluble sulfate, nitrate, chloride oraliphatic monocarboxylic acid salt of a metal selected from the groupconsisting of lead and metals from Groups IB, IIB, VIB, VIIB, and VIIIof the Periodic Table; wherein the carboxylic acid polymer ischaracterized as having a carboxylic acid monomer content in the rangeof from 20 to 100 mol percent, a number average molecular weight of atleast 5,000 and a solubility in water at a pH of less than 7 of at least1% by weight at 25° C.; wherein the salt has a water solubility of atleast 1% by weight at a pH less than 7; and wherein said aliphaticmonocarboxylic acid contains 1 to 4 carbon atoms.
 2. The composition ofmatter as in claim 1 wherein the soluble metal salt is selected from thegroup consisting of acetates and formates of manganese, nickel,chromium, copper, cobalt and lead.
 3. A composition of claim 1 whereinthe polymer is a maleic anhydride copolymer having a comonomer selectedfrom the group consisting of vinyl acetate, ethylene and vinyl methylether.
 4. A composition of matter as in claim 1 wherein the metal saltis zinc acetate.
 5. A composition of claim 1 which further includes apolyacrylamide flocculating atent.